Commercial hot air impingement cooking apparatus

ABSTRACT

Various representative commercial cooking devices are disclosed wherein a recirculating flow of heated air, at a food cooking temperature, is created within a housing in which a horizontally disposed food support and cooking member, such as a perforated metal plate, a solid griddle plate or a metal broiling grate, is positioned. A plenum structure is utilized to convert a portion of the continuously recirculated air into a spaced series of relatively high velocity heated air impingement jets which are caused to laterally diffuse and at least slightly overlap prior to striking at least one side surface of the food support structure. In this manner, each food support structure side surface subjected to such diffused jet impingement is evenly blanketed with heating air to thereby very uniformly transfer heat from the air to the food support structure, and thus to the food supported thereby, at an accelerated rate.

This application is a division of application Ser. No. 279,094, filedDec. 2, 1988, now U.S. Pat. No. 4,972,824, issued Nov. 27, 1990.

BACKGROUND OF THE INVENTION

The present invention relates generally to cooking apparatus and, invarious preferred embodiments thereof, more particularly providescommercial hot air impingement cooking apparatus which, compared toconventional commercial cooking devices such as pizza hearth ovens,frying griddles, convection ovens and broiling grills, provides avariety of advantages.

Conventional commercial cooking devices of the types representativelylisted above are subject to a variety of well known disadvantages andlimitations including relatively high fabrication and operating costs,lengthy pre-cooking warmup time, undesirable variation in batch-to-batchcooking times, uneven heat transfer to the food items being cooked,and/or the inability to vary the relative cooking rates of upper andlower portions of the food items.

A prime example of a commercial cooking device which is subject to avariety of these disadvantages and limitations is the stone hearth ovenused to cook pizzas. The stone hearths used in these ovens to supportand cook the pizzas is typically approximately 11/2" thick and takesapproximately two hours to be preheated from room temperature to itsapproximately 500° F. operating temperature. Because of this elongatedwarmup time, it is conventional practice, while the pizza establishmentis closed during the night, to very uneconomically maintain the oven ata holding temperature of approximately 300° F. so that the warmup timeat the beginning of the next business day is reduced to an acceptablyshort time.

Because of the very substantial thermal lag unavoidably associated withthese thick stone hearths, there is a substantial variation in batchcooking times. For example, the first batch of pizzas cooked in a givenbusiness day, after the stone hearth has been preheated to its 500° F.operating temperature, takes approximately 10 minutes. However, the nextbatch typically takes approximately 12 minutes, and the succeedingbatches take approximately 15 minutes each.

Additionally, there is typically no provision for varying the relativecooking rates of the pizza crust and its topping ingredients.

It is accordingly an object of the present invention to provide improvedcommercial cooking apparatus which eliminates or minimizesabove-mentioned and other disadvantages and limitations typicallyassociated with commercial cooking devices such as pizza ovens, fryinggriddles, convection ovens and broiling grills.

SUMMARY OF THE INVENTION

In carrying out principles of the present invention, a variety ofrepresentative commercial cooking apparatus embodiments are provided inwhich a recirculating flow of heated air is created within a housinghaving at least one relatively large area food support and cookingstructure horizontally disposed therein. Plenum means are verticallyspaced apart from the food support structure and function to convert aportion of the recirculating air into a spaced series of relatively highvelocity vertically directed heated air jets which transversely impingeupon at least one of the opposite side surfaces of the food support andcooking structure.

The jets are caused to laterally diffuse and at least slightly overlapprior to striking their associated food support structure side surface,thereby evenly blanketing such side surface with transversely directedheated impingement air. In this manner, heat from the recirculating airis very evenly transferred to the food support structure, and to fooditems supported thereby, at an accelerated rate to very uniformly andrapidly cook the food items regardless of their positions on the foodsupport structure, and without the necessity of moving the food itemsduring the cooking process.

In the present invention, this very even distribution of heating air jetimpingement flow is incorporated in the following representativeembodiments:

1. Various single and multi-tier pizza cooking ovens in which the foodsupport structures are perforated thin metal cooking plates and theuniformly distributed impingement jet flow is directed against theopposite upper and lower side surfaces of each plate;

2. A countertop oven in which the food support structure is a thin metalperforated plate and the uniformly distributed impingement jet flow isdirected against the opposite upper and lower side surfaces of theplate;

3. Half-sized convection ovens in which the food port structures aremetal cooking racks each positioned between oppositely directed seriesof laterally diffusing heated air impingement jets;

4. An air impingement frying griddle in which the underside of a largearea, relatively thin metal griddle plate is subjected to theaforementioned evenly distributed flow of laterally diffusing heated airimpingement jets;

5. A dual griddle impingement air cooker in which the food items arepositioned between upper and lower relatively thin metal griddle platespositioned between oppositely directed series of laterally diffusingheated air impingement jets; and

6. A clamshell grill in which the food items being cooked are pressedbetween upper and lower metal grate members which are positioned betweenoppositely directed series of laterally diffusing heated air impingementjets.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a perspective view of a single tier pizza cooking slot ovenembodiment of the present invention;

FIG. 2 is an enlarged scale cross-sectional view through the slot oventaken along line 2--2 of FIG. 1;

FIG. 3 is a cross-sectional view through the slot oven taken along line3--3 of FIG. 2;

FIG. 4 is an enlarged scale perspective view of one of the heated airsupply plenum structures used in the slot oven;

FIG. 5 is a partial cross-sectional view through the supply plenumstructure, taken along line 5--5 of FIG. 4, and illustrates itsoperation in conjunction with a perforated food support and cookingplate portion of the slot oven;

FIGS. 6 and 7 are cross-sectional views, respectively similar to thosein FIGS. 3 and 2, through a double tier embodiment of the slot oven withits lower tier being operated;

FIGS. 8 and 9 are cross-sectional views similar to those in FIGS. 6 and7, but with the oven's upper tier being operated;

FIG. 10 is a perspective view of a side-by-side multiple tier pizza ovenembodiment of the present invention;

FIG. 11 is a cross-sectional view through the pizza oven taken alongline 11--11 of FIG. 10;

FIG. 12 is a somewhat schematic exploded perspective view of theinternal heated air supply portion of the left side of the pizza oven asviewed in FIG. 10;

FIG. 13 is an enlarged scale partial cross-sectional view through theupper tier air supply and return plenum structure depicted in FIG. 12,and is taken along line 13--13 of FIG. 12;

FIG. 14 is an enlarged scale cross-sectional view through the pizza oventaken along line 14--14 of FIG. 110;

FIG. 15 is a perspective view, partially in phantom, of a countertopoven embodiment of the present invention;

FIG. 16 is a cross-sectional view through the countertop oven takenalong line 16--16 of FIG. 15;

FIG. 17 is a cross-sectional view through the countertop oven takenalong line 17--17 of FIG. 16;

FIG. 18 is a perspective view of a half-size convection oven embodimentof the present invention;

FIG. 19 is an enlarged scale perspective view of one of the removableair impingement supply plenum structures used in the convection oven;

FIG. 20 is a partial cross-sectional view through the convection oventaken along line 20--20 of FIG. 21;

FIG. 21 is an enlarged scale cross-sectional view through the convectionoven taken along line 21--21 of FIG. 18, the oven's supply plenumstructures and their support brackets having been removed forillustrative purposes;

FIG. 22 is a partial cross-sectional view through the convection oventaken along line 22--22 of FIG. 21;

FIG. 23 is a downwardly directed cross-sectional view through analternate embodiment of the convection oven;

FIG. 24 is a cross-sectional view through the alternate convection ovenembodiment taken along line 24--24 of FIG. 23;

FIG. 25 is a perspective view of an air impingement griddle embodimentof the present invention;

FIG. 26 is an enlarged scale cross-sectional view through the griddletaken along line 26--26 of FIG. 25;

FIG. 27 is a partial cross-sectional view through the griddle takenalong line 27--27 of FIG. 26;

FIG. 28 is a partial cross-sectional view through the griddle takenalong line 28--28 of FIG. 27;

FIG. 29 is a side cross-sectional view through an alternate embodimentof the air impingement griddle;

FIG. 30 is a partial cross-sectional view through the alternate griddleembodiment taken along line 30--30 of FIG. 29;

FIG. 31 is a perspective view of a clamshell grill embodiment of thepresent invention;

FIG. 32 is an enlarged scale cross-sectional view through the grilltaken along line 32--32 of FIG. 31; and

FIG. 33 is an exploded perspective view of drop-in air return, heating,and air supply sections used in the grill.

DETAILED DESCRIPTION

The present invention, in various preferred embodiments thereof,provides commercial recirculating hot air impingement apparatus used tocook a variety of food items. As will be seen from the detaileddescriptions of the representative invention embodiments set forthbelow, a central theme of the present invention is the use of arecirculated flow of heated air to create a very evenly distributedtransverse flow of relatively high velocity heated impingement air ontoat least one generally horizontal side surface of a large area, heatconducting food support structure from one or more supply plenum devicesvertically spaced apart from the food support structure.

Air delivery from the supply plenum devices is preferably in the form ofa mutually spaced series of heated impingement air jets which are causedto laterally expand or "plume" prior to transversely striking theirassociated side surface of the food support structure (and, as the casemay be, the supported food product as well) in a manner such thatessentially the entire area of such side surface above or below thesupply plenum device is evenly "blanketed" with transversely directedimpingement cooking air.

This very uniform horizontal distribution of transversely directedimpingement cooking air across essentially the entire verticallyprojected area of the food support structure side surface or surfacesabove or below the plenum provides a variety of advantages overconventional commercial cooking devices used to cook the same products.For example, it permits the food support structure to take the form of athin metal plate (either solid or perforated, depending on theparticular cooking application) having a very low mass compared toconventional food support structures such as stone pizza cookinghearths, thick metal frying griddles and the like. Coupled with thetransverse air impingement and its even distribution across the quitelarge cooking areas commonly provided in commercial cooking devices, thethin plate provides for much more rapid and even heat transfer to thefood product being cooked, thereby markedly reducing cook cycle and heatup times. While the thin plate configuration of the food supportstructure provides a variety of benefits, the air impingement anddistribution principles of the present invention may also beadvantageously utilized in conjunction with more massive food supportstructures such as metal grill grates.

An important additional advantage of the present invention is that thefood product being cooked does not in any manner have to be movedtransversely to the air impingement jets during the cooking process toassure even cooking of the food. Moreover, regardless of the position onthe large area food support structure that a particular food item isplaced, it will be rapidly and very uniformly cooked while in astationary position within the particular cooking apparatus.

The very simple air-only heating scheme employed in the presentinvention also permits the various commercial cooking devices describedbelow to be, in most instances, constructed at a significantly lowercost than conventional commercial apparatus used to cook the same foodproducts.

Importantly, however, the various benefits described above are achievedin the present invention without in any manner reducing the quality ofthe cooked food end product. Indeed, it has been found in developing thepresent invention that such quality is, in many instances, significantlyenhanced. Turning now to the drawings, various preferred embodiments ofthe present invention will be described in detail.

Pizza Cooking Slot Oven

The single tier pizza cooking slot oven 10 illustrated in FIGS. 1-3comprises a housing 12 which is floor supportable on wheels 14 or legsand is provided with internally insulated, double sided exterior wallsincluding top wall 16, front wall 18, rear wall 20, left side wall 22,right side wall 24, and bottom wall 26. A horizontally extending,vertically intermediate wall 28 divides the housing interior into anupper section having a cooking chamber 30 therein, and a lower sectionhaving a heating and air supply chamber 32 therein. Access to thecooking chamber 30 is provided by a swing-down closure and observationdoor 34 mounted on front wall 18, and access to the lower chamber 32 isprovided by front and side access panels 36 and 38.

Within the lower housing section, a vertical dividing wall 40 extendingbetween the opposite side walls of the lower housing section cooperateswith a pair of dividing walls 42 and 44 extending rearwardly from thewall 40 to the rear housing wall 20 to define within the chamber 32 leftand right fan motor chambers 46 and 48 (FIG. 3) at the rear corners ofthe lower housing section, and a heating chamber 50 positioned betweenthe fan motor chambers 46 and 48. A pair of fan motors 52 and 54 arerespectively supported within the chambers 46 and 48, and are used todrive centrifugal fan impellers 56 and 58 positioned within fandischarge plenums 60 and 62 supported within the heating chamber 50 onthe dividing walls 42 and 44. A suitable fuel burner 64 or electricelement package (not illustrated) is extended through the dividing wall40 into the heating chamber 50 and is utilized to supply heat theretofor purposes subsequently described.

Spaced upwardly from the intermediate wall 28 is a horizontal supportwall 66. Secured to wall 66, and extending upwardly therefrom, are fourelongated divider plates 68 which longitudinally extend in aleft-to-right direction across the cooking chamber 30. The upper sideedges of the plates 68 support a thin metal cooking support plate ordeck 70 having a series of circular holes 72 formed transverselytherethrough. In the illustrated preferred embodiment of the perforateddeck 70, its thickness is approximately 1/16", and the holes 72 have1/4" diameters and are spaced apart on staggered 1/2" centers.

Deck 70 defines with the divider plates 68 and the support wall 66front, center and rear baffle plenums 74, 76 and 78. Respectivelysupported on the wall 66 within the baffle plenums 74, 76 and 78 arethree elongated metal supply plenum boxes 80, 82 and 84 which are eachspaced downwardly from the deck 70. These lower supply plenum boxes 80,82 and 84 are of identical construction which will now be described withreference to the supply plenum box 84 perspectively illustrated in FIG.4.

Supply plenum box 84 is of a hollow, elongated rectangular configurationand has an inlet opening 86 formed in its right end wall 88. Theelongated rectangular top wall of the plenum box 84 is provided withtransversely extending corrugations as illustrated, the corrugationshaving a spaced series of generally V-shaped, upwardly projecting ridges90. A spaced series of elongated rectangular air discharge slots 92 areformed in each of the ridges 90.

Supported from the top housing wall 16 in a vertically spacedrelationship with the deck 70 are a pair of supply plenum boxes 94 and96. The upper plenum box 94 is positioned over the front lower plenumbox 80, while the upper plenum box 96 is positioned over the lowercenter plenum box 82. Upper plenum boxes 94, 96 are substantiallyidentical in configuration to the lower plenum boxes except that theirinlet openings 98 (FIG. 3) are positioned in their left end walls, andthe interior cross section of the plenum box 94 is substantially largerthan the interior cross sections of the other four plenum boxes. Thelower side walls of the upper plenum boxes 94, 96 are transverselycorrugated and are provided with downwardly projecting ridges 100 havingelongated rectangular air discharge slots 102 formed therein.

During operation of the pizza cooking slot oven 10, with a pizza 104supported on the perforated deck 70, air within the heating chamber 50(FIG. 3) is heated by the products of combustion 106 (FIG. 2) emanatingfrom the burner 64 or electric elements (not illustrated) and is drawninto the fans 56 and 58 through inlet openings 108 and 110 formed in thefan discharge plenums 60 and 62. Heated air 112 entering the inletopening 108 is discharged by the fan 56 through a supply duct 114 thatextends upwardly through the wall 28 and extends below the support wall66 to a vertical supply passage 116 formed inwardly along the lefthousing side wall 22. Heated air 112 upwardly traversing the supplypassage 116 is forced into the inlet openings 98 of the upper supplyplenum boxes 94 and 96 via discharge openings 117. The heated air 112forced into the interior of the upper supply plenum boxes 94 and 96 isdischarged downwardly through their ridge slots 102 in the form ofrelatively high velocity heated air jets 118 which, in a mannersubsequently described, laterally diffuse and impinge upon the uppersurface of the pizza 104 and the deck 70 in a manner evenly blanketingthe portions of such surfaces beneath plenum boxes 94, 96 with atransverse flow of heated impingement air.

Heated air 120 (FIG. 3) entering the fan 58 is discharged therefromthrough a supply duct 122 that extends upwardly through the wall 28 andextends below the support wall 66. Duct 122 terminates at a verticalsupply passage 124 that extends upwardly along the inner surface of theright housing wall 24 and terminates at the inlet openings 86 of thelower supply plenum boxes 80, 82 and 84. Heated air 120 forced into theinterior of these lower supply plenum boxes is upwardly dischargedtherefrom, through their ridge slots 92, in the form of relatively highvelocity heated air jets 126.

As illustrated in FIGS. 4 and 5, these upwardly directed jets 126laterally diffuse, or "plume", prior to striking the underside of theperforated deck 70. The jets 126 thus tend to at least somewhat overlapprior to transversely striking the underside of the deck 70, therebyevenly blanketing the deck underside with heated impingement air. In asimilar fashion, the downwardly directed upper jets 118 (FIGS. 2 and 3)laterally diffuse in a manner evenly blanketing the upper surfaceportions of the deck and the pizza 104 beneath the upper plenum boxeswith transversely directed heated impingement air.

A portion of the diffused jets 126 striking the underside of the deck 70pass through underlying deck openings 72 onto the underside of the pizza104, while the balance of the diffused jets 126 are forced upwardlythrough others of the holes 72 in the form of upwardly directed airstreams 128. The air streams 128, and the downwardly directed jets 118after they have impinged upon the upper surfaces of the pizza and thedeck 70, are drawn rearwardly, as return air 130, (FIGS. 2 and 3) into aseries of horizontally elongated rectangular return openings 132 formedin the interior side surface of the rear housing wall 20 between thedeck 70 and the upper supply plenum boxes 94 and 96. Return air 130entering the openings 132 is drawn downwardly through a vertical returnpassage 134, formed in the rear housing wall 20, and into the heatingplenum 50 via an elongated return slot 136 formed in the intermediatewall 28. Return air entering the heating chamber 50 is heated by theburner 64 or electric elements (not illustrated) and drawn into the fans56 and 58 to maintain the recirculating flow of heated air through thehousing 12 as previously described.

The diffused, evenly blanketed transverse impingement of the jets 92 and118 on the opposite sides of the perforated deck 70 and the upper sidesurface of pizza 104, and the horizontal return air flow over the top ofthe pizza, function to very uniformly cook the pizza in a fraction ofthe time required by conventional stone hearth cooking ovens. Thecombination of this diffused, vertical impingement, which acceleratesheat transfer to the pizza 104, and the generally horizontal flow ofreturn air 130 across the top of the pizza 104, provides thissignificantly reduced cooking time, while at the same time maintaining avery high quality in the finally cooked pizza.

The perforated deck 72 is of a larger-than-standard commercial size (56"wide by 36" deep in the illustrated embodiment), and the housing 12 isof a standard commercial size (approximately 63" wide, 45" deep and 51"high) so that the slot oven 10 may be easily and quickly used to replacea standard stone hearth pizza oven.

The oven 10 provides a variety of advantages over conventional stonehearth pizza cooking ovens. The standard pizza oven now widely in useutilizes a 48" by 36" stone hearth cooking deck which typically has a11/2" thickness. Typically, no more than four 16" diameter standardpizzas can be efficiently cooked on the stone hearth. However, despiteits standard sized floor "footprint", the oven 10 of the presentinvention can simultaneously cook six standard 16" diameter pizzas onits enlarged 56" by 36" perforated deck.

In the standard pizza oven, its stone cooking hearth typically requiresa warmup time of approximately two hours to be heated from roomtemperature to the typical operating temperature of approximately 500°F. As a practical matter, in most conventional pizza operations, thestone hearth oven is continuously operated at a reduced temperatureapproximately 300° F.) when the establishment is closed to reduce thisrather lengthy warmup time on the next business day. In sharp contrast,the pizza cooking oven 10 of the present invention may be heated fromroom temperature to a similar 500° operating temperature inapproximately 30 minutes. This very significantly reduces the totalwarmup and cooking time for the first batch of pizzas cooked in a givenbusiness day. It also eliminates the necessity to operate the oven at anintermediate holding temperature when the pizza establishment is closed.The oven 10 can simply be turned on approximately one half hour beforethe establishment opens, and will be brought from room temperature tothe approximately 500° F. operating temperature when the business daystarts.

In the conventional stone hearth oven, the very first batch of fourpizzas is typically cooked in approximately 10 minutes. However, thesecond batch of four pizzas typically takes approximately 12 minutes,due to the thermal lag inherent in the stone hearth, and subsequentfour-pizza batches take approximately 15 minutes each. However, in theoven 10 of the present invention, due to the very rapid heat up of thethin metal perforated deck, the first and each succeeding batch of sixpizzas are cooked in approximately 6 minutes-there is no correspondingincrease in the batch cooking times as in the case of the conventionalstone hearth oven.

Importantly, due to the fact that the oven 10 of the present inventionis able to cook half again as many pizzas in a given batch as aconventional stone hearth oven, and, on the average, cooks the pizzas insomewhat less than half the time, the production capacity of the oven 10is at least twice and potentially three times that of the conventionalstone hearth oven.

It is also important to note that in the conventional stone hearth oven,it is not feasible to vary the amount of heat transferred to the pizzacrust from the stone hearth relative to the amount of heat transferredto the top of the pizza from radiation within the oven. However, in theoven 10 of the present invention, this variation in upper side heattransfer to the pizza versus lower side heat transfer from the metaldeck, can be very easily varied simply by selectively varying the airdelivery from the fans 56 and 58. For example, to increase the relativeheating of the upper side of the pizza, the speed of fan 56 is simplyincreased. In a similar fashion, to increase the metal deck heat to thepizza crust, the speed of the fan 58 is increased.

While particularly well suited to the cooking of pizzas, the oven 10 isalso quite well suited to cooking a variety of other food productsranging from pastry items to a variety of meat products.

Cross-sectionally illustrated in FIGS. 6-9 is an alternate, dual tierembodiment 10_(a) of the previously described slot oven 10. For purposesof comparison, the reference numerals of the elements of oven 10_(a)similar to those in oven 10 have been given the subscript "a" or "b".The slot oven 10_(a) is generally similar in operation to the previouslydescribed oven 10 except that the housing 12_(a) is provided with aninsulated dividing wall 136 which divides the upper housing section intoan upper tier or cooking chamber 30_(a) and a lower "tier" or cookingchamber 30_(b). In a manner subsequently described, the upper cookingchamber 30_(a) is operated by the fan 58_(a), and the lower cookingchamber 30_(b) is operated by the fan 56_(a). The upper and lowercooking chambers 30_(a), 30_(b) may be operated simultaneously orindependently as desired and are provided with separate swing-downaccess and observation doors 34_(a), 34_(b) mounted on the front housingwall 18_(a). The upper and lower cooking chambers 30_(a) and 30b arerespectively provided with upper supply plenum boxes 138 and 140 whichare secured to the upper housing wall 16_(a) as illustrated. These upperplenum boxes are similar in configuration to the upper plenum boxespreviously described, except that they extend across the entire widthand depth of the cooking chambers 30_(a) and 30b. The inlet 98_(a) ofplenum box 138 extends along its right side, while the inlet 98_(b) ofplenum box 140 extends along its left side as viewed in FIGS. 6 and 8.

The support walls 66_(a) and 66_(b) respectively support lower plenumboxes 142 and 144 within the cooking chambers 30_(a) and 30b. The inletopenings 86_(a) of plenum box 142 is positioned along its right side,while the inlet 86_(b) of the plenum box 144 is positioned along itsleft side. The plenum boxes 142 and 144 extend along the entire widthand front-to-rear depth of the cooking chambers 30_(a) and 30b. Thinmetal perforated cooking decks 70_(a) and 70_(b) are supported above theplenum boxes 142 and 144 in the cooking chambers 30_(a) and 30b bysuitable support members 146.

As illustrated in FIGS. 6 and 7, during operation of the lower cookingchamber 30b, the fan 56_(a) is energized to flow heated return air 148through supply duct 114_(a) upwardly through a vertical supply passage150 into the inlets 98_(b) and 86_(b) of the plenum boxes 140 and 144 tocreate the hot air impingement jets 118_(b) and 126_(b) which arediffused and transversely strike the opposite upper and lower sidesurfaces of the perforated deck 70_(b) as previously described inconjunction with the slot oven 10. After such impingement, the resultingair flow 130b is drawn rearwardly into an elongated rectangular returnslot 132_(b) formed in the rear housing wall 20_(a), and is floweddownwardly into the heating chamber 50_(a) through a vertical returnpassage 152 (FIG. 7) and the wall opening 136_(a).

Referring now to FIGS. 8 and 9, during operation of the upper heatingchamber 30_(a), the fan 58_(a) is energized to draw heated air 154 intothe fan discharge plenum 62_(a) and force the air 154 upwardly through avertical supply passage 156 into the inlets 98_(a) and 86_(a) of theupper cooking chamber plenum boxes 138 and 142. The heated supply airreceived in the interiors of the plenum boxes 138 and 142 is forcedoutwardly through their air discharge slots 102_(a) and 92_(a) to formthe heated air impingement jets 118_(a) and 126_(a) which impinge uponthe opposite sides of the upper perforated deck 70_(a). The resultingturn air flow 158 is drawn rearwardly into an elongated return air slot132_(a) formed in the rear housing wall 20_(a) and flowed downwardlythrough a vertical return passage 160 and into the heating plenum 50_(a)through the opening 136_(a) in the wall 28_(a).

In this manner, either or both of the cooking chambers 30_(a) and 30bmay be operated as desired. Control of the fans 52_(a) and 54_(a) andthe heating temperature of the recirculated air flowed into and out ofthe cooking chambers 30_(a) and 30b may be conveniently controlled via acontrol panel mounted on the front wall of the housing 12_(a) andsimilar to the control panel 162 (FIG. 1) used in conjunction with theslot oven 10.

Side-by-Side Multiple Tier Pizza Oven

The side-by-side multiple tier pizza oven 170 illustrated in FIGS. 10-14includes a pair of insulated metal housings 172 and 174 positioned in aside-by-side relationship, each of the housings having an upper section176 and a lower section 178. Disposed within each of the upper housingsections 176 are four or more vertically stacked plenum box structures180 (FIG. 12) which are divided by partition walls 182 into a frontsupply sections 184 and rear return sections 186. As best illustrated inFIGS. 11 and 12, the stacked sets of plenum box structures 180 arelaterally spaced apart, and are provided with facing side walls 188 inwhich rectangular supply inlet openings 190 and rectangular returnoutlet openings 192 are formed. In each of the plenum box structures180, the supply opening 190 communicates with the interior of the supplysection 184, and the return outlet opening 192 communicates with theinterior of the return section 186.

Referring now to FIGS. 12 and 13, each of the plenum box structures 180has a front wall 194 with a horizontally elongated opening 196 formedtherein and leading into the interior of the front supply section 184 sothat a pizza may be inserted therein and supported and cooked in amanner subsequently described. The interior of the front supply section184 is provided with an internal wall structure 198 (FIG. 13) whichdefines the front side opening 196 and comprises a corrugated upper wall200, a corrugated lower wall 202, and a right side wall 204 whichinterconnects the right side edges of the walls 200, 202 as illustratedin FIG. 13. The left side edges of the walls 200, 202 are secured to theleft side wall 206 of the plenum box structure 180, and the rear sideedges of the walls 200, 202 and 204 are secured to the partition wall182. A baffle plate member 208 projects horizontally from a verticallyintermediate portion of the wall 204 to define with the walls 200, 202and 204 an upper supply plenum 210 and a lower supply plenum 212 withinthe plenum box structure 180.

The vertically spaced upper and lower corrugated walls 200 and 202 arerespectively provided with downwardly projecting, generally V-shapedridges 214, and upwardly projecting, generally V-shaped ridges 216.Along their front-to-rear lengths, the downwardly facing ridges 214 haveformed therein spaced series of elongated rectangular air dischargeslots 218. In a similar manner, the upwardly projecting ridges 216 haveformed along their front-to-rear lengths series of elongated rectangularair discharge slots 220.

Supported between the ridges 214 and 216 by mounting support brackets222 is an 18"×18" thin metal plate or cooking deck 224 in which a spacedseries of circular openings 226 is formed. In the illustrated embodimentof the deck 224, its thickness is approximately 1/16", and the openings226 are 1/4" circular holes positioned on staggered 1/2" centers. Asillustrated, the deck 224 is considerably closer to the lower corrugatedwall 202 than to the corrugated upper wall 200. Positioned verticallybetween the upper wall 200 and the perforated deck 224 are threeelongated rectangular return openings 228 which are formed in thepartition wall 182 and intercommunicate the interior of the rear returnsection 186 with the interior of the wall structure 198 between theupper wall 200 and the perforated deck 224.

As best illustrated in FIG. 10, each of the upper housing sections 176is provided along its front side with four swing-down doors 230 whichmay be opened to provide access to the food insertion and withdrawalopening 196 of its associated plenum box structure 180, and may beclosed to cover such opening 196. For purposes later described, each ofthe plenum box structures is provided with its own control panel section232, the control panels 232 being positioned along the front wall of theoven 170 between the vertical rows of doors 230. Each of the controlpanel sections 232 is representatively provided with a "cook" button234, a corresponding cooking indicating light 236, a "warm" button 238and a corresponding indicating light 240, and a timer set dial 242.

Referring now to FIG. 14, the lower sections 178 of the side-by-sidehousings are provided with walled off air handling sections 244 and 246which are divided by partition walls 248 and 250 into fan plenums 252,254 and return plenums 256, 258. Centrifugal fan impellers 260 and 262positioned in the fan plenums 252, 254 communicate with the returnplenums 256, 258 through return openings 264, 266 and are driven bymotors 268, 270. Communicating at their lower ends with, and extendingupwardly from the return plenums 256, 258 are a pair of verticallyextending return passages 272 and 274 which are positioned between therear return sections 186 of the stacked series of plenum box structures180 as illustrated in FIG. 11. In a similar manner, the lower ends of apair of vertically extending supply ducts 276, 278 communicate with thefan plenums 252, 254 and extend upwardly between the stacked series ofplenum box structure 180 in alignment with the supply inlet openings 190therein.

As representatively illustrated in FIG. 12, each of the supply ducts276, 278 is provided with four branch outlet sections 280, each alignedwith one of the inlet openings 190. Interposed between each of thebranch outlet sections 280 and its associated supply box inlet opening190 is a slide plate damper member 282 which may be selectively moved ina front-to-rear direction, as indicated by the arrows 284, by means ofsmall actuating motors 286 linked to the damper members 282 by actuatingrods 288. Each of the damper members 282 has solid front and rearportions 282_(a), 282_(b), between which a rectangular opening 282_(c)is formed.

When a particular damper member 282 is in its rearwardly moved closedposition, its solid portions 282_(a), 282_(b) cover and block the inletand outlet openings 190, 192 of its associated plenum box structure 180.When the damper member is moved forwardly to an open position, thedamper opening 282_(c) is aligned with the plenum box opening 190 andthe plenum box opening 192 is uncovered.

During operation of the pizza oven 170, with the fans 260, 262 beingoperated, one of the doors 230 is swung downwardly to its open positionas depicted in FIG. 10, thereby uncovering the front opening 196 of oneof the plenum box structures 180. A pizza 288 to be cooked is positionedatop the perforated deck 224 in the opened plenum box structure. Theopened door 230 is then closed and the cook button 234 associated withthe particular plenum box structure is pushed. This causes the plenumbox structure's damper member 282 to automatically be moved forwardly toits open position so that heated air 290 is flowed inwardly from theduct supply branch 280 into the inlet opening 190 through the upper andlower portions thereof formed by the baffle plate member 208. The heatedair 290 is thus forced into the upper and lower supply plenums 210 and212 where it is discharged downwardly and upwardly through the dischargeslots 218, 220 in the form of relatively high velocity heated airimpingement jets 292 and 294 (FIG. 13).

The jets 292 and 294 laterally diffuse after their discharge from theslots 218, 220 and transversely impinge upon the upper side surface ofthe deck 224 and the pizza 288, and the lower side surface of the deck224. This laterally diffusion, or "pluming", of the jets 292 and 294causes them to at least slightly overlap and therefore evenly blanketthe deck and pizza surfaces upon which they transversely impinge. Aportion of the lower jets 294 pass upwardly through the deck openings226 directly onto the lower surface of the pizza, while the remaininglower jets 294 are passed upwardly through the remaining deck openings226 to create the upward air flow indicated by the arrows 296. The airflow 296 mixes with the air flow from the jets 292 after they haveimpinged upon the upper deck and pizza surfaces to form a return airflow 298 which is drawn rearwardly through the return openings 228 intothe return portion 186 of the plenum box structure 180 in which thepizza 288 is being cooked (see FIG. 11). The return air flow 298 isdrawn outwardly through the return outlet 192 and is drawn into thereturn duct 272 through a suitable opening 300 therein. As illustratedin FIG. 14, the return air flow 298 drawn downwardly through the returnduct 272 exits its open bottom end and is drawn across one of a pair ofelectric heating coils 302 to form the heated air 290 which is drawninto the fan 260 and supplied via the supply duct 276 to the particularplenum box structure 180. In this manner, a continuous flow ofrecirculated heated air is delivered into and from the selected plenumbox structure 180.

When the cooking time for the pizza 288 in its selected plenum boxstructure 180 is completed, as determined by the setting of theparticular timer dial 242, the appropriate damper member 282 isautomatically moved rearwardly to its closed position, therebyterminating the heated air inflow through the inlet opening 190, and theheated air outflow through the return outlet 192 of the plenum boxstructure. This automatically energizes the plenum box's warming light240 to indicate that the pizza 288 is fully cooked. A slight amount ofair leakage through the plenum box's inlet and outlet openings maintainsthe cooked pizza in a "warming mode" until it is removed from itsperforated deck 224.

A considerable degree of flexibility is built into the illustratedmultiple tier pizza oven 170. For example, its side-by-side halves maybe independently or simultaneously operated depending on whether one orboth of the fans 260, 262 is operated. During operation of either of thefans 260, 262, its associated supply duct 276 is continuouslypressurized at an essentially constant pressure awaiting the opening ofone or more of its associated damper members 282. Accordingly, in eitherhalf of the oven 170, from one to several pizzas may be in variousstages of their overall cooking cycles, each of such cycles beingautomatically controlled and terminated so that the particular pizza orpizzas are conveniently kept warm until they are removed for delivery tothe customer.

The previously described diffused air impingement pattern directed at arelatively high velocity onto opposite sides of selected ones of theperforated decks 224 provide for extremely rapid yet very uniformcooking of the pizza or pizzas, while at the same time maintaining avery high quality of the resulting food product. This is true regardlessof where on its perforated deck 224 the particular pizza is placed, andthere is no necessity whatever to move the pizza about in its cookingchamber to assure this even cooking of the pizza. The transverseimpingement of the heated air onto the perforated deck provides anaccelerated rate of air-to-deck heat transfer which provides forextremely rapid warmup times without the relatively long delaysencountered with, for example, conventional stone pizza cooking hearths.

Countertop Oven

The countertop oven 310 depicted in FIGS. 15-17 comprises an insulatedmetal housing 312 which is conveniently sized to rest on a kitchencountertop and has top and bottom walls 314 and 316, left and right sidewalls 318 and 320, a rear wall 322, and a front wall 324 provided with aswing-down closure and observation door 326. Within a left side portionof the housing 312, partition walls 328 and 330 form a motor chamber 332and a control chamber 333. Extending between the rear and front walls322, 324, and spaced rightwardly of the partition wall 328 is a bafflestructure 334 which defines with the partition wall 328 a fan chamber336. A centrifugal fan impeller 338 is operatively positioned in the fanchamber 336 and is rotationally driven by a drive shaft 340 connected toa fan motor 342 disposed within the motor chamber 332.

A pair of vertically spaced, horizontally positioned upper and lowerplate members 344 and 346 extend between the baffle structure 334 andthe right housing wall 320, and between the rear and front housing walls322 and 324. The plates 344, 346 define with the top and bottom housingwalls 314, 316 an upper supply plenum 348 and a lower supply plenum 350.Supply plenums 348, 350 respectively communicate with the fan chamber336 via passages 352 and 354 disposed above and beneath the bafflestructure 334. A pair of electric heating elements 356 extend from thepartition wall 328 into the lower supply plenum 350 through the passage354, and a pair of heating elements 358 extend from the partition wallinto the upper supply plenum 348 through the passage 352.

The upper and lower plates 344, 346 define therebetween a cookingchamber 358 that communicates with the inlet of the fan impeller 338through a tapered opening 360 formed through the baffle structure 334.The opening 360 has positioned therein a suitable flow control damper362.

A right side portion of the upper plate 344 is corrugated as at 364 toform downwardly projecting, generally V-shaped ridges 366 that extendbetween the rear and front housing walls 322, 324. Each of thesedownwardly projecting ridges 366 is provided with a spaced series ofelongated rectangular air discharge slots 368. In a similar fashion,most of the left-to-right length of the lower plate 346 is corrugated toform a series of upwardly projecting, generally V-shaped ridges 370,each of such ridges being provided along its front-to-rear length with aspaced series of elongated rectangular air discharge slots 372.

Supported above the lower plate member 346, just below the bafflestructure return opening 360, is a thin metal cooking plate or deck 374having formed therethrough a series of circular openings 376. Theillustrated deck 374 is approximately 1/16" thick, and is of anelongated rectangular configuration, having a 13" left-to-right widthand an 18" front-to-rear length. These dimensions are each one half ofthe stand commercial oven cooking area size. The holes 376 have 1/4"diameters, and are spaced apart on staggered 1/2" centers. As can bebest seen in FIG. 17, the deck 374 is considerably closer to the lowerplate 346 than it is to the upper plate 344.

The countertop oven 310 is controlled via a suitable control panel 378(FIG. 15) mounted on the front wall 324 over the control chamber 333,and is operated as follows. A desired food product contained, forexample, in a cooking pan 380 is placed atop the perforated deck 374,the door 326 is closed, and the oven is energized to operate the fan 338and the heating elements 356 and 358. Air within the fan chamber 336 isforced by the fan 338 through the passages 352, 354 across the heatingelements 358 and 356 into the upper and lower supply plenums 348 and 350in the form of heated air 382 and 384.

The heated air 382 and 384 is forced downwardly and upwardly through theair discharge slots 368 and 372 in the form of relatively high velocityheated air impingement jets 386 and 388. The upper jets 386 laterallydiffuse, or "plume", prior to their transverse impingement upon a rightside portion of the food product within the pan 380 and a right sideportion of the upper surface of the perforated deck 374, thereby evenly"blanketing" these right side surface portions with transverselydirected heated impingement air.

The lower jets 388 also laterally diffuse or "plume" prior to strikingthe underside of the perforated deck 374. In this manner, the lower jets388 overlap at least to a small degree, thereby evenly blanketing theunderside of the deck 374 with transversely directed heated impingementair. Some of the lower jets 388 pass upwardly through the deck openings376 and impinge upon the bottom side of the pan 380. The remainder ofthe lower jets 388, and the air downwardly deflected from the deck areabelow the pan, are flowed upwardly through the rest of the deck openings376 and mix with the upper jets 386 after their impingement upon the panand deck, to form a return air flow 390 which is drawn horizontallyacross the pan 380 into the inlet of the fan 338 through the bafflestructure opening 360. This returning air flow is then forced outwardlyfrom the fan into the upper and lower supply plenums 348, 350 tomaintain a recirculated flow of heating air through the oven housing.The flow rate of such recirculating heating air may be easily regulatedby appropriate adjustment of the damper 362. Similarly, the temperatureof such recirculated air may be regulated by suitable control of theupper and lower heating elements 358 and 356.

The laterally diffused, transversely directed flow of the upper andlower jets 386, 388 onto opposite side surfaces of the deck 374, andonto the upper surface of the food product and the lower surface of thepan 380, coupled with the very even lateral distribution of theimpingement air flow on such surfaces functions to very rapidly cook thefood product in a fraction of the time required in conventional air flowovens. The rapid cooking of the food product is achieved, however,without the necessity of moving the food product during the cookingcycle or diminishing the quality of the finally cooked food product.

Half-Size Air Impingement Convection Oven

The half-size air impingement convection oven 400 illustrated in FIGS.18-22 has an insulated metal housing 402 having a front wall 404, a rearwall 406, and top wall 408, a bottom wall 410, a left side wall 412, anda right side wall 414. As best illustrated in FIGS. 20 and 22, aninsulated vertical partition wall 416 is spaced inwardly from the rightside wall 414 and forms therewith a motor and burner chamber 418 withina right side portion of the housing 402. A generally L-shaped hollowmetal baffle structure 420 is positioned within the housing and has avertically extending, elongated rectangular front portion 422 spacedleftwardly from the partition wall 416, and a hollow rectangular baseportion 424 which extends rightwardly from the bottom of the portion 422through the partition wall 416 into the chamber 418.

The front baffle portion 422 has a front side wall 426, a rear side wall428, a pair of opposite side edge walls 430 and 432, which are spacedinwardly from the housing walls 406 and 404, and a top edge wall 434which is spaced downwardly from the top housing wall 408. At the bottomof the front baffle structure portion 422 are a pair of leg portions 436(FIG. 21) which define therebetween a rectangular opening 438. Legs 436are joined to corresponding leg portions 440 (FIG. 22) of the bafflestructure base portion 424. Three horizontally elongated rectangularinlet openings 442 are formed in the front side wall 426, and a circularoutlet opening 444 is formed in the rear wall 428.

A centrifugal fan impeller 446 (FIGS. 20 and 21) is positioned betweenthe partition wall 416 and the front portion 422 of the baffle structure420, and is driven by a motor 448 positioned in the chamber 418. Alsopositioned in the chamber 418 is a fuel burner 450 (FIG. 22) which isextended into the base portion 424 of the baffle structure 420.Positioned between the baffle structure front portion 422 and the lefthousing wall 412 is a cooking chamber 452 to which access is provided bya closure and observation door 454 (FIG. 18) mounted on the fronthousing wall 454 immediately to the left of a control panel section 456thereon.

During operation of the convection oven 400, the burner 450 forcesproducts of combustion 458 through the base portion legs 440 andupwardly through the front portion legs 436 into the interior of thebaffle structure front portion 422. The hot products of combustion aremixed with air 460 drawn by the fan 446 from the cooking chamber 452into the interior of the baffle structure front portion 422 through itsrectangular inlet openings 442. The air 460 heated in this manner isdrawn through the baffle structure outlet opening 444 into the inlet ofthe fan 446. The heated air 460 drawn into the fan 446 is thenvertically discharged into the cooking chamber 52 across the top andside edges of the baffle structure front portion 422, and through itsbottom opening 438. Before entering the baffle structure inlet openings442 for mixture with and heating by the products of combustion 458, theair 460 within the cooking chamber 452 is forced into and through threeair impingement cooking plenum boxes 462 which will now be described inconjunction with FIGS. 18-20.

Each of the cooking plenum boxes 462 is of an elongated rectangularmetal construction and has top and bottom side walls 464 and 466 a leftend wall 468, a right end wall 470 having a horizontally elongatedrectangular outlet opening 472 formed therein and of the same size asthe baffle structure wall openings 442, a closed rear side wall 474, andan open front side 476. A 13"×18" food support rack 478 is removablysupported within each cooking plenum box 462 on suitable supportbrackets 480. The rack 478 is positioned just below the outlet opening472 and is considerably closer to the bottom corrugated wall 466 than tothe top corrugated wall 464.

The corrugations in the top wall 464 are provided with a series ofdownwardly projecting, generally V-shaped ridges 482, each of suchridges having formed therein along its length a spaced series ofelongated rectangular air discharge slots 484. In a similar manner, thebottom corrugated wall 466 is provided with a series of upwardlyprojecting, generally V-shaped ridges 486 in each of which is formed aspaced series of elongated rectangular air discharge slots 488.

Referring now to FIGS. 18 and 20, three vertically spaced pairs ofsupport brackets 492, 494 are respectively secured to the walls 412, 426within the cooking chamber 452. Each of the cooking plenum boxes 462 isremovably insertable into the cooking chamber 452 as indicated by thedouble-ended arrow 496 in FIG. 18, and is supported by the brackets 492and 494 as illustrated in FIG. 20. Each of the cooking plenum boxes 462,when inserted in the cooking chamber 452 in this manner, is spacedsomewhat forwardly from the rear housing wall 406 by means of setofftabs 498 (FIG. 19) secured to the rear wall of the plenum box. With thehousing door 454 in its closed position, the door covers the open frontside 476 of each of the plenum boxes.

During operation of the oven 400, heated air 460 flowed into the cookingchamber 452, as previously described is forced downwardly and upwardlyinto the interior of each of the plenum boxes 462 through the dischargeslots 484 and 486 and enters the interior of the plenum box in the formof downwardly directed heated air impingement jets 500, and upwardlydirected heated air impingement jets 502 as best illustrated in FIG. 20.The upper and lower jets 500, 502 laterally diffuse, or "plume", beforestriking the upper side surfaces of the food support rack 478 in amanner evenly blanketing its opposite side surfaces with transverselydirected heated impingement air. Accordingly, the upper and lower sidesurfaces of, for example, a cooking pan 504 supported on the rack 478are similarly subjected to a highly uniform flow of relatively highvelocity, heated air impingement flow to very rapidly and evenly cook afood product supported in the pan.

The heated air entering the plenum box 462 illustrated in FIG. 20 isdrawn horizontally rightwardly across the rack 478 and the food pan 504through the plenum box outlet opening 472 which is aligned with one ofthe baffle structure wall openings 442. The return air exiting theplenum box is then flowed through the baffle structure portion 422 andinto the fan 446 as previously described.

While the plenum boxes 462 just described function to very rapidly andevenly cook a variety of food items which may be operatively disposedtherein, one or more of the plenum boxes may be removed and temporarilyreplaced with a conventional cooking rack 506 (FIG. 20) to utilize aportion of the oven 400 as a more conventional convection oven withoutthis impingement air feature.

Cross-sectionally and somewhat schematically illustrated in FIGS. 23 and24 is an alternate embodiment 400a of the previously described airimpingement convection oven 400. For purposes of ready comparison,components in the alternate oven embodiment 400a similar to those in theoven 400 have been given the same reference numerals, but with thesubscripts "a".

In the oven 400_(a), the baffle structure is eliminated, and the fan446a is positioned within a return plenum 562 defined between apartition wall 508 and the partition wall 416a. Partition wall 508 isprovided with three vertically spaced, horizontally elongatedrectangular inlet openings 510. The fan 446a is housed within adischarge plenum 512 that communicates with a supply plenum 514 formedwith the rear housing wall 406a by a vertical partition wall 516 havingfour horizontally elongated rectangular outlet openings 518 formedtherein. Upper and lower corrugated baffle walls 520 and 522 are formedacross the cooking chamber 452a to form supply plenums 524 and 526 thatrespectively communicate with the upper and lower wall openings 518. Thecorrugations in the upper and lower baffle walls 520, 522 respectivelyhave downwardly and upwardly projecting, generally V-shaped ridges 528,530 which are provided with spaced series of elongated rectangulardischarge slots 532, 534. Secured to the left housing wall 412a and thepartition wall 508 within the cooking chamber 452a are three verticallyspaced pairs of support channel members 536, each pair of whichhorizontally supports a cooking rack 538. The lower cooking rack 538 isspaced a short distance above the lower corrugated baffle wall 522.

The upper two support channel member pairs 536 also support, beneath theupper two racks 538, a pair of supply plenum box members 540. Each ofthe supply plenum boxes 540 has an open rear side positioned against thepartition wall 516 over one of its openings 518, a closed front wall,left and right end walls 542 and 544, a corrugated upper side wall 546,and a lower corrugated side wall 548. The corrugations in the upper sidewalls 546 are provided with upwardly projecting, generally V-shapedridges 550 having spaced series of elongated rectangular air dischargeslots 552 formed therein, while the corrugations in the lower box walls548 have downwardly projecting, generally V-shaped ridges 554 withspaced series of elongated rectangular air discharge slots 556 formedtherein.

During operation of the oven 400_(a), the heated air 460_(a) (which isheated by electric resistance heating elements or a suitable fuel burnernot illustrated) is forced by the fan 446_(a) into the rear side supplyplenum 514 and is then forced forwardly through the partition walloutlet openings 518 into the supply plenums 524 and 526, and into theinteriors of the plenum boxes 540. Such heated air is then forcedoutwardly through the previously described air discharge slots in theform of downwardly directed heated air impingement jets 558, andupwardly directed heated air impingement jets 560.

As can be seen in FIG. 24, each of the three support racks 538 ispositioned between opposing sets of jets 558 and 560, the racks 538being positioned substantially closer to their associated source ofupwardly directed jets than to their associated source of downwardlydirected jets. Each set of jets 558, 560 laterally diffuse and overlapprior to transversely striking the opposite upper and lower sidesurfaces of the racks 538 and food items or food containers supportedthereon. In this manner, the racks are very evenly blanketed withtransversely directed heated impingement air to provide for very rapidand even cooking of food products within the cooking chamber 452_(a).After it performs such impingement functions, the heated air flow460_(a) is drawn horizontally rightwardly into he partition wallopenings 510 into the return plenum 562, within which the fan 446_(a) ispositioned, and is drawn into the fan inlet for recirculated flow intothe heating chamber 452_(a) as previously described.

Air Impingement Cooking Griddle

The air impingement cooking griddle 570 shown in FIGS. 25-28 utilizes asolid, thin metal griddle plate 572 to fry food items 574 supportedthereon. Griddle plate 572 has an elongated rectangular configurationand is provided around its periphery with an upturned metal lip 576. Thegriddle plate is received in a complementarily configured opening 578formed in the top wall 580 of an insulated metal housing 582. Inaddition to the top wall 580, the housing 582 has left and right sidewalls 584 and 586, a front wall 588, a rear wall 590, and an elevatedinterior bottom wall 592. The griddle plate 574 is supported within thehousing opening 578 by means of a spaced series of horizontallyextending, elongated rectangular support plates 594 (FIGS. 26 and 27).

Positioned below the support plates 594, and supported on elongatedrectangular plates 596, are three air supply plenum boxes 598. Theplenum boxes 598 have elongated rectangular configurations, arepositioned in a laterally spaced relationship, and, as best illustratedin FIG. 27, extend lengthwise across the width of the griddle plate 574above. Each of the plenum boxes 598 is provided with a corrugated upperwall whose corrugations have upwardly projecting, generally V-shapedridges 600 in which spaced series of elongated rectangular air dischargeslots 602 are formed.

A fan plenum 604 is supported on the interior housing wall 592 beneaththe plenum boxes 598, and is positioned between a motor chamber 606 atthe front of the housing 582 and a heating chamber 608 spaced forwardlyof the rear wall 590 of the housing 582. Heating chamber 608 has a rearwall 610 in which a pair of circular return air openings 612 are formedat its opposite ends as best illustrated in FIG. 28. The front wall 614of the heating chamber 608 has a circular opening 616 formed thereinwhich communicates with the interior of the fan plenum 604. Asillustrated in FIG. 28, the heating chamber outlet opening 616 ispositioned horizontally between the return air opening 612, and a pairof electric resistance heating coil elements 618 are positioned betweenthe return air openings 612 and the heating chamber outlet opening 616.A centrifugal fan impeller 620 is positioned within the fan plenum 604,and is driven by a motor 622 positioned in the motor chamber 606.

Extending outwardly from the fan plenum 604 are three branch supplyducts 624 which are extended upwardly through the bottom walls 626 ofthe supply plenum boxes 598. The open upper ends of the branch supplyducts 624 are positioned beneath baffle plates 628 positioned within theplenum boxes and supported in an elevated position relative to thebottom plenum box walls 626 by small support members 630.

During operation of the griddle 570, air 632 behind the heating chamber608 is drawn inwardly into the heating chamber through its rear wallopenings 612, is flowed across the heating elements 618 to heat the air,and then is drawn into the fan 620 through the heating chamber outletopening 616. The heated air 632 is then flowed upwardly through thebranch supply ducts 624 into the interiors of the supply plenum boxes598. The air entering the plenum supply boxes is diffused upwardlyaround the baffle plates 628 and is forced out of the corrugation slots602 in the form of upwardly directed heated air impingement jets 632.

The upwardly directed impingement air jets 634 laterally diffuse, or"plume", before transversely striking the lower side surface of thegriddle plate 574. In this manner the upwardly directed jets 632 arecaused to at least slightly overlap, thereby very evenly blanketing theunderside of the griddle plate to thereby very uniformly transfer heatthereto at an accellerated rate to fry the food items 574 supportedthereon. After the jets 632 impinge upon the griddle plate in thismanner, a return flow of the air 632 (see FIG. 27) is drawn downwardlybetween the plenum boxes 598, and rearwardly beneath the griddle plate,and then is returned to the heating chamber 608 through the rear wallopenings 610 as previously described to maintain a continuousrecirculating flow of heated air through the housing 582.

The unique combination of the thin griddle plate 574 and the diffusedtransverse flow of impingement jet air which uniformly blankets itslower side surface provides for very rapid heatup of the griddle plate574, and further provides for extremely even heat distribution acrossits entire length and width. The griddle plate 574 may be easily andquickly removed from the upper housing opening 578 for purposes ofcleaning, and may be quickly reinserted into such opening 578. Theillustrated air impingement griddle 570 is very economical to fabricate,and is quite simple and efficient to operate. If desired, theillustrated electric heating coil elements 618 could be replaced with aconventional fuel fired heating system.

An alternate embodiment 570_(a) of the griddle 570 is illustrated inFIGS. 29 and 30 and comprises an insulated metal housing 640 having abase section 644 with an open upper end, and a lid section 646 which ispivoted to the upper end of the base section 644, as by a rear mountedhinge element 648, and has an open lower side. The lid section 646 isprovided with a front mounted handle 650 which may be used to pivot thelid section about hinge 648 between the illustrated closed position ofthe lid section and an open position in which the lid section is pivotedin a clockwise direction about the hinge.

An upper griddle plate 652 is suitable secured within the open lowerside of the lid section 646, and a lower griddle plate 654 is removablypositioned within the open upper end of the housing base section 644 andsupported on a spaced series of horizontally extending support plates656. A lower supply plenum 658 is defined beneath the support plates 656within the base housing section 644 by a horizontal partition wall 660,and a corrugated lower partition wall 662 positioned above the wall 660.A suitable electric resistance heating coil element 664 is positionedwithin the lower supply plenum 658. The corrugations of the partitionwall 662 are provided with upwardly projecting, generally V-shapedridges 666 in which are formed spaced series of elongated rectangularair discharge slots 668.

A centrifugal fan impeller 670 is operatively disposed within a fanplenum 672 positioned in the housing base section 644 adjacent the rearwall thereof, the fan 670 being driven by a suitable motor 674. A supplyduct 676 is extended between the interior of the lower supply plenum 658and the outlet of the fan plenum 672, and a return duct 678intercommunicates the inlet of the fan 670 with the space 678 betweenthe lower corrugated partition wall 662 and the lower griddle plate 654.

An upper corrugated partition wall 680 extends across the interior ofthe housing lid section 646 above the upper griddle plate 652, and formswithin the lid section an upper supply plenum 682 positioned above thecorrugated wall 680. A suitable electric resistance heating coil element684 is positioned within the upper supply plenum 682. The corrugationsin the upper partition wall 680 have downwardly projecting, generallyV-shaped ridges 686 in which are formed spaced series of elongatedrectangular air discharge slots 688.

A fan plenum housing 690 is externally mounted on the upper wall 692 ofthe lid section 646 adjacent its back side. A centrifugal fan impeller694 is mounted within the plenum housing 690 and is driven by a motor696 supported on the upper housing wall 692 by a suitable support member698. The fan plenum 690 is extended downwardly through the upper housingwall 692 and is connected to an open-ended supply duct 700. A returnduct 702 is connected at its upper end to the interior of the fan plenumhousing 690, extends downwardly through the upper housing wall 692, andhas an open lower end 704 positioned in the space 706 between the uppercorrugated partition wall 680 and the upper griddle plate 652.

The griddle 570_(a) is operated by opening its lid section 646 anddepositing food items to be cooked, such as hamburgers 708 on the lowergriddle plate 654. The lid section 646 is then closed to bring the uppergriddle plate 652 into contact with the upper sides of the hamburgers708. The fans 670 and 694, and the heating elements 664 and 684 are thenenergized.

Operation of the lower fan 670 forces air 710 through the supply duct676 upwardly into the lower supply plenum 658. Air 710 entering thelower supply plenum 658 is horizontally diffused by a baffle platemember 712 and forced upwardly across the heating element 664. Theheated air 710 is then forced upwardly through the air discharge slots668 in the form of spaced series of upwardly directed heated airimpingement jets 714. The jets 714 laterally diffuse, or "plume", beforetransversely striking the underside of the lower griddle plate 64. Thispluming of the jets 714 causes them to at least slightly overlap beforethey transversely strike griddle plate 654. This causes the transverselydirected impingement air to evenly blanket the underside of the lowergriddle plate, thereby very evenly transferring heat thereto acrossessentially the entire length and width of the lower griddle plate.After the heated air has transversely impinged upon the lower griddleplate in this manner, the air 710 is drawn downwardly through the returnduct 678 and into the lower fan 670 to thereby maintain a constantrecirculating flow of heated air through the housing base section 644.

Operation of the upper fan 694 forces air 716 through the supply duct700 into the upper supply plenum 682 and across the upper heatingelement 684. The heated air 716 is then forced downwardly through theair discharge slots 688 in the upper corrugated partition wall 680 toform a spaced series of downwardly directed heated air impingement jets718 which, like the previously described lower jets 714, laterallydiffuse and overlap, and transversely strike the upper side surface ofthe upper griddle plate 652. In this manner, impingement air heat isvery evenly spread across such upper side surface of the griddle plate652 to transfer heat thereto in an extremely uniform pattern and at ahighly accelerated rate. After the downwardly directed jets 718impingement upon the upper griddle plate 652, the deflected air 716 isdrawn horizontally across the space 706 and is flowed upwardly throughthe return duct 702 into the fan 694 to provide a continuousrecirculating flow of heated air through the lid section 646 of thehousing 640.

From the foregoing, it can be seen that the upper and lower griddleplates 652, 654 which are evenly heated on their inner side surfaces bythe impingement air jets 714 and 718 simultaneously fry the hamburgers708 on their opposite sides in a very efficient, speedy manner.

Air Impingement Grill

Illustrated in FIGS. 31-33 is an air impingement grill 730 which has aninsulated metal housing having a base section 732 with an open upperend, and a lid section 734 which has an open lower side and is pivotallysecured to the base section 732 by a rear mounted hinge member 736. Avertically extending interior partition wall 738 divides the interior ofthe housing base section 732 into a front motor chamber 740 and a rearwell area 742 into which specially fabricated fan, heating and returnhousings 744, 746 and 748 may be downwardly and removably insertedthrough the open upper end of the housing base section 732.

The fan housing 744 has an open upper end 750 and has disposed therein acentrifugal fan impeller 752 which is connectable, via a drive shaft 754to a motor 756 mounted in the motor chamber 740. The fan impeller 752 issurrounded within the housing 744 by a discharge scroll structure 758,and the rear side wall 760 of the housing 744 is provided with acircular opening 762 which is positioned over the inlet of the fan 752.

The heating housing 746 has a circular opening 764 formed in a right endportion of its front side wall 766 which is aligned with the opening 762in the fan housing 744, a circular opening 768 formed in a left endportion of its rear side wall 770, and an electric resistance heatingelement 772 positioned horizontally between the openings 764 and 768.

The return housing 748 has an elongated rectangular inlet collar 774projecting upwardly from its upper side wall 776, and a circulardischarge opening 778 formed in its front side wall 780, the opening 778being aligned with the opening 768 in the rear wall 70 of the heatinghousing 746. A drop-in wire mesh basket filter element 782 isoperatively received within the inlet collar 774, projects downwardlyinto the return housing 748, and rests upon a support flange 784internally secured to the rear wall 786 of the return housing 748. Withthe housing lid section 734 pivoted to its open position, the filterelement 782 may be simply lifted upwardly through the open upper end ofthe inlet collar 774 for inspection and cleaning purposes.

A downwardly and forwardly sloping corrugated partition wall 788 extendsacross the interior of the housing lid section 734 and defines with theupper wall 790 of the lid section an upper supply plenum 792. Supplyplenum 792 communicates with the open upper end of the supply scrollsection 760 via a vertical passage 794 formed in the left side wall 796of the lid section 734. An upper cooking grate member 798 is supportedwithin the lid section 734, below the corrugated wall 788, for verticalmovement within the lid section by pivotally mounted support arms 800.The corrugations in the upper partition wall 788 define downwardlyprojecting, generally V-shape ridges 802, each of which has formedtherein a series of spaced apart elongated rectangular air dischargeslots 804.

A forwardly and downwardly sloped lower corrugated partition wall 806 issupported within the open upper end of the housing base section 732 in adownwardly spaced relationship with a lower cooking grate member 808also supported within the open upper end of the housing base section732. The lower corrugated partition wall 806 defines the upper boundaryof a lower supply plenum 810 which communicates with the open upper endof the fan discharge scroll structure 758. A baffle plate 812 issupported in the supply plenum 810, by small support members 814 in anupwardly spaced relationship with the open upper end 750 of the fanhousing 744. The corrugations in the lower partition wall 806 defineupwardly projecting, generally V-shaped ridges 816 in which spacedseries of elongated rectangular air discharge slots 818 are formed.

During operation of the grill 730, with a food item such as a steak 820pressed between the upper and lower grate members 798 and 808, the fan752 forces air 822 upwardly into the upper and lower supply plenums 792and 810. The air 822 entering the lower supply plenum 810 is laterallydiffused by the baffle plate 812 and is forced outwardly through thedischarge slots 818 in the form of a series of upwardly directed heatedair impingement jets 824. In a similar manner, air 822 entering theupper supply plenum 792 is forced downwardly through the air dischargeslots 804 in the form of a series of downwardly directed heated airimpingement jets 826. The jets 824, 826 laterally diffuse, or "plume",and slightly overlap before transversely impinging upon the gratemembers 798, 808 and the opposite side surfaces of the steak 820,thereby evenly blanketing these opposite side surfaces with a uniformpattern of transversely directed impingement air to rapidly and veryevenly cook the steak from opposite sides.

After such impingement on opposite sides of the food product beingcooked, and the upper and lower support grates, a return flow of air 822is drawn downwardly through the filter element 782 into the returnhousing 748. The air 822 then flows outwardly through the circularopening 778 and into the interior of the heating housing 746 through itsrear wall opening 768. The air is then drawn across the heating element772 and flowed outwardly through the heating housing outlet opening 764into the inlet of the fan 752 for upward discharge through the dischargescroll 758 as previously described. In this manner, a continuous flow ofrecirculating heating air is maintained within the housing of the grill730 in a manner very rapidly and evenly cooking the steak 820.

The foregoing detailed description is to be clearly understood as beinggiven by way of illustration and example only, the spirit and scope ofthe present invention being limited solely by the appended claims.

What is claimed is:
 1. A multi-tiered air impingement cooking ovencomprising:a housing having positioned therein a vertically stackedseries of air plenum boxes, each of said air plenum boxes having:aninternal cooking chamber, an essentially flat, relatively large areaperforated food support and cooking member horizontally supported withinsaid cooking chamber and adapted to support a food item within saidcooking chamber, a front opening through which a food item may be placedon and removed from said food support and cooking member, upper airsupply plenum means positioned above said food support and cookingmember for receiving pressurized air from a source thereof andconverting the received air into a spaced series of downwardly directed,relatively high velocity air jets which laterally diffuse prior tostriking and evenly blanketing the upper side surface of said foodsupport and cooking member to transfer air heat thereto at anaccelerated rate, lower air supply plenum means positioned below saidfood support and cooking member for receiving pressurized air from asource thereof and converting the received air into a spaced series ofupwardly directed, relatively high velocity air jets which laterallydiffuse prior to transversely striking and evenly blanketing the lowerside surface of said food support and cooking member to transfer airheat thereto at an accelerated rate, an inlet opening communicating withsaid upper and lower supply plenum means, and an outlet passagecommunicating with said cooking chamber between said food support andcooking member and said upper plenum means; heated air recirculatingmeans operable to create within said housing a recirculating flow ofheated air which operatively traverses at least one of said air plenumboxes, said heated air recirculating means including:an air supplypassage having an inlet, and a series of outlets each positioned to flowair into one of said inlet openings of said air plenum boxes, a returnpassage adapted to receive air discharged from said outlet passages ofsaid air plenum boxes and having an outlet end, a fan operativelyinterconnected between the inlet of said air supply passage and theoutlet end of said return passage, and heating means for heating airrecirculated by said fan to a food cooking temperature; and controlmeans for controlling heated air flow through each of said air plenumboxes, said control means including:a series of damper members eachassociated with one of said air plenum boxes and movable between aclosed position in which air flow through the inlet opening and outletpassage of its air plenum box is substantially precluded, and an openposition in which air flow through the inlet opening and outlet passageof its air plenum box is permitted, means for opening a selected numberof said damper members to initiate in their associated air plenum boxesa cooking cycle having a predetermined duration, and means forautomatically closing each opened damper member at the completion of thecooking cycle time of its associated plenum box.
 2. The cooking oven ofclaim 1 wherein:said upper and lower supply plenum means arerespectively provided with lower and upper corrugated walls with ridgeswhich project toward their associated food support an cooking member andare vertically spaced apart therefrom, said ridges having formed thereinseries of spaced apart rectangular air discharge openings.
 3. Thecooking oven of claim 2 wherein:in each of said air plenum boxes thefood support and cooking member is positioned substantially closer toits associated lower plenum means than to its associated upper plenummeans.
 4. The cooking oven of claim 1 wherein:each of said food supportand cooking members is a relatively thin perforated metal plate member.5. The cooking oven of claim 4 wherein:each of said plate members has anapproximately 18" by 18" square configuration.
 6. The cooking oven ofclaim 1 wherein:each of said air plenum boxes has a vertical side wallextending transversely to said side opening, said side wall having saidinlet opening and an outlet opening formed therein, and an internalpartition wall having at least one air return opening formed therein andseparating said upper and lower plenum means from a return chamberpositioned within the air plenum box and opening outwardly through saidoutlet opening.
 7. The cooking oven of claim 6 wherein:each dampermember is an elongated plate member having a central opening andoverlying the vertical sidewall of its associated air plenum box formovement therealong between its open and closed positions.
 8. Thecooking oven of claim 1 wherein:said fan and heating means arepositioned in a lower portion of said housing, said air plenum boxes arepositioned in an upper portion of said housing, and said air supply andreturn passage extend vertically between said air plenum boxes and saidfan.
 9. The cooking oven of claim 1 further comprising:a second housingpositioned in a side-by-side relationship with said first-mentionedhousing, said second housing having components therein substantiallyidentical to those in said second housing but arranged in a mirror imagetherewith.